As diimidas naftálicas simétricas têm sido vastamente estudadas devido suas propriedades químicas, ópticas, e eletrônicas. A possibilidade de modular suas propriedades com a substituição de grupos diversos na formação da imida, viabiliza aplicações em dispositivos eletrônicos, conversão de energia e produção de redes de coordenação metalo-orgânicas. Neste trabalho sintetizou-se uma série de 5 diimidas naftálicas (NDIs) simétricas com substituintes aromáticos. Foram analisadas as características espectroscópicas e eletrônicas com obtenção dos valores de band-gap óptico através de ensaios de voltametria cíclica e cálculos teóricos (DFT), mostrando a influência dos substituintes nas propriedades eletrônicas. Estas moléculas apresentam indícios de agregação em determinados solventes tornando possível a produção de filmes finos. As NDIs produzidas foram intercaladas em uma matriz inorgânica lamelar, o pentóxido de vanádio amorfo, e melhorando consideravelmente, via de regra, a capacidade específica de carga quando analisados em sistemas trocadores de íon lítio, aplicados geralmente em cátodos de bateria, com valores da ordem de 190 mA.h.g-1 (sob 100 uA, variação de E +1,2V à -1,2V). É provavelmente um dos primeiros trabalhos a utilizar NDIs em sistemas mistos de matrizes inorgânicas aplicados em trocadores de íons. Algumas apresentam potencial para dispositivos de conversão de luz em eletricidade. / Symmetric naphthalic diimides have been extensively studied due to their chemical, optical, and electronic properties. The possibility of modulating their properties by substitution with several groups in the formation of imides allows diverse applications in electronic devices, energy conversion, production of metallo-organic frameworks (MOFs). In this thesis, a series of 5 symmetrical aromatic-substituted naphthalic diimides (NDIs) were sinthesized. We have studied their optical and electronic characteristics obtaining optical band-gap with cyclic voltammetry tests and theoretical calculations (DFT), showing the influence of substituent in the electronic properties. Some of these imides may aggregate in certain solvents allowing this way the production thin films. The NDIs were intercalated in the inorganic intercalation matrix of amorphous vanadium pentoxide, and showed generally considerable improvement in the specific charge capacity when used in lithium ion exchange systems, that are usually applied in battery cathodes, reaching values of the order of 190 mA.h.g-1 (under 100 uA, E variation of + 1.2V to -1.2V). This is probably one of the first works using NDIs in mixed systems to applied inorganic matrices as ion exchangers. Some of them may be used for light conversion to electricity devices.

Neste trabalho foi preparado e caracterizado estruturalmente um novo compósito de pentóxido de vanádio xerogel (XRG-V2O5) e gelatina na proporção de 1 e 10% em massa (gelatina/V2O5). O xerogel obtido foi submetido a secagem (80, 200 ou 300°C) sob pressão reduzida por 4 horas. A caracterização estrutural consistiu de medidas de difração de raios-X (DRX), espectroscopia FTIR e Raman, análise termogravimétrica (TGA) e microscopia eletrônica de varredura (MEV). Técnicas de voltametria cíclica a baixa velocidade de varredura e curvas cronopotenciométricas foram também aplicadas para investigação do comportamento deste xerogel frente a eletrointercalação de íons lítio. Foi observado que os compósitos XRGV2O5/gelatina possuem basicamente a mesma estrutura local do XRG-V2O5, ou seja são constituídos por pirâmides distorcidas de base quadrada VO5. Os compósitos também apresentam organização bidimensional com formação de camadas, semelhante ao XRG-V2O5 pristino. A gelatina encontra-se no material inserida entre as camadas do xerogel, e sua presença altera significativamente o valor da distância basal, não sendo esta distância diminuída com o aumento da temperatura de tratamento térmico. A gelatina também afeta o grau de desordem do xerogel. Os resultados sugerem que a gelatina presente no interior do material encontra-se em conformações segundo a concentração de H2O no mesmo. Os compósitos mostraram-se aptos a intercalar íons lítio eletroquimicamente. Os XRG-V2O5/gelatina preparados com 1% de gelatina, e em particular a amostra submetida ao tratamento térmico a 200°C, fornecem capacidades específicas superiores àquelas encontradas na literatura para o XRG-V2O5 pristino (capacidades específicas superiores a 120 mA.h/g). Também verificou-se que a gelatina não participa dos processos de transferência de carga com o lítio. / In this work it was prepared and characterized structurally a new composite of vanadium pentoxide xerogel (XRG-V2O5) and gelatin in rate of 1 and 10% in weight (gelatin/V2O5). The xerogel obtained was submitted to drying (80, 200 or 300°C) under vacuum for 4 hours. The structural characterization consisted of X-ray diffraction (XRD), FTIR and Raman spectroscopy, termogravimetric analysis (TGA) and scanning electronic microscopy (SEM) measures. Techniques of cyclic voltametry at low scan rate and chronopotenciometric curves also were applied to investigate the behavior of this xerogel front the electrointercalation of lithium ions. It was observed that the composites XRG-V2O5/gelatin have the same local structure of XRG-V2O5, being constituted by VO5 distorted square pyramids. The composites also show a two-dimensional organization with formation of layers, similar to the pristine XRG-V2O5. The gelatin is inserted in the material among the xerogel layers, and its presence alters the basal distance values significantly. This distance weren\'t decreased with the temperature increase of thermal treatment. The gelatin also affects the degree of xerogel disorder. The results suggest that gelatin inside the material is in conformation according to H2O concentration at xerogel. The composites are able to insert lithium ions electrochemically. XRGV2O5/ gelatin prepared with 1% of gelatin, in particular the sample submitted to the thermal treatment to 200°C, provide higher specific capacities that those found in the literature for pristine XRG-V2O5 (specific capacities superiors than 120 mA.h/g). It was also verified that gelatin doesn\'t participate of charge transfer processes with lithium.

A síntese, caracterização e propriedades de um novo compósito xerogel formado por óxido de vanádio e óxido de silício, com alta concentração de vanádio foi o objetivo deste trabalho. O compósito xerogel foi obtido mediante a formação de uma rede complexa envolvendo a condensação de polioxovanadato em meio aquoso com concomitante hidrólise e condensação de um alcóxido de silício. Conseqüentemente, este método possibilitou a obtenção de um material multicomponente homogêneo, no qual a rede Si O Si está interpenetrada com as cadeias poliméricas V-O- V e V-OH-V, promovendo uma solubilidade mútua, devido a formação de ligações cruzadas. Além disso, resultados experimentais apontam que, mesmo após a imobilização em matriz de sílica, a estrutura bi-dimensional, bem como as propriedades eletroquímicas do xerogel de pentóxido de vanádio são preservadas. A atividade catalítica do material obtido também foi avaliada na oxidação do cicloocteno e do estireno na fase líquida. O compósito xerogel V2O5/SiO2 obtido com tetraetiltrietóxisilano (TEOS), mediante catálise básica, o qual apresentou área superficial elevada (324 m2/g), e apresentou atividade catalítica em reações de oxidação do estireno e do cicloocteno na presença de PhIO como doador de oxigênio. Contudo, estes materiais apresentaram propriedades eletroquímicas inferiores as do xerogel de pentóxido de vanádio. Por outro lado, o comportamento eletroquímico óxido misto obtido com metiltrietóxisilano (MTES) é muito similar ao xerogel de V2O5; apresentando picos reversíveis ( par redox VV/IV: xe- + xLi+ + V2O5.nH2O ? LixV2O5.nH2O, em solução de LiClO4 0,1 mol.L -1 em acetonitrila). Além disso, a resposta eletroquímica á estável mesmo após sucessivos ciclos de oxidação e redução. Um aspecto interessante é que este compósito é formado por partículas esféricas de sílicas recobertas por xerogel de pentóxido de vanádio Neste contexto, pode-se afirmar que, o método empregado mostrou-se extremamente atrativo devido a sua simplicidade de realização, além de possibilitar um novo método de obtenção de materiais com potencial aplicação como dispositivos eletroquímicos, baterias, catalisadores e sensores químicos. / The synthesis, characterization and properties of new vanadium oxide silicon oxide composite xerogels with high vanadium content through formation of a complex network involving the condensation of polyoxovanadates in aqueous solution with concomitant hydrolysis and condensation of the silica alkoxide precursor have been the goal of this work. As a consequence, this procedure generated a homogeneous multicomponent material, in which Si-O-Si network is interpenetrated with V-V and V-OH-V polymeric chains, where a mutual \"solubility\" due to cross-links and entanglements was observed. In addition, the experimental data evidence that the vanadium pentoxide xerogel embedded in silica retains its bi-dimensional structure as well as its electrochemical properties. Besides, the catalytic activity of this material was evaluated in the oxidation of the cyclooctene and styrene in liquid phase. V2O5-SiO2 composite xerogels obtained from tetraethoxysilane under basic catalysis, present high surface area (324 m2/g) and have catalytic activities in alkene oxidation in the presence of PhIO as oxygen transfer agent and cyclooctene and styrene as substrates. However, these materials do not present a remarkable electrochemical property as evidenced by cyclic voltammetry. In contrast, the voltammetric behavior of the composites xerogel prepared with methyltriethoxysilane is quite similar to that found for V2O5 xerogel; showing reversible peaks (VV/IV redox pair: xe- + xLi+ + V2O5.nH2O LixV2O5.nH2O, in acetonitrile solutions containing 0.1 M LiClO4). Besides, the electrochemical response is stable under several successive redox cycles (over 50). An interesting feature is that is formed by silica spherical particles (4 to 8 micra) covered with V2O5 continuous polymeric network. Therefore, the synthetic approach applied in this study is extremely attractive due to its simplicity and can provide new strategies for tailoring new materials for electrochromic devices, batteries, catalysis and chemical sensing.

Background Vanadium is an economically important mineral that is mined and processed at several international locations, including South Africa and the USA. Vanadium exists in several oxidative states, of which the pentavalent compounds are usually the most toxic. Vanadium pentoxide (V205) is pentavalent and is generated during various processing and metal alloy manufacturing processes. Occupational exposure may occur via inhalation of V205 fumes and particles, resulting primarily in adverse effects to the respiratory system. Currently, there is no evidence that vanadium is carcinogenic in humans, and it has never been reported in exposed humans. The International Agency for Research in Cancer (IARC) has classified V205 as possibly carcinogenic to humans, based on the increased incidence of bronchiolo-alveolar neo¬plasms observed in male and female mice and male rats in a study by the National Toxicology Program (NTP) of the US Department of Health and Human Services. The NTP study has prompted the international vanadium industry, embodied by Vanitec, the international association of vanadium producers, to request an epidemiological study with the aim of determining the potential association between cancer and occupational V205 exposure. Aim The aim of the study was to conduct a pilot retrospective case-control study to investigate the relationship between cumulative occupational exposure to V2O5 and the risk of developing cancer at two representative vanadium processing plants, one in SA and one in the USA. Methods All cases and controls were sourced from the industry’s current and past employee corps. Employees that could potentially have been exposed to V2O5 in the workplace for a period of at least 5 years were included in the study. Ethics approval for the study was obtained from the Ethics Committee of the University of Pretoria. Participation was on a voluntary basis, and all potentially eligible current workers were invited to participate. As many retirees and former employees as possible were traced and invited to participate, and eligible deceased employees that conformed to the inclusion and exclusion criteria were identified from lists provided by the companies involved. Potential participants were asked to grant informed consent to participate in the study. Health and lifestyle information, information on fuel use in the family home, and a personal job history were obtained by use of a structured questionnaire during a personal interview with a trained interviewer. Interviews were conducted from April to July 2004. The main inclusion criterion for both cases and controls was current or previous employment at the South African, or the USA vanadium processing facility included in the study. The disease case definition was histologically confirmed cancer. Exclusion criteria were: refusal of interview; less than 5 years in employment when V2O5 was produced at the plant; cause of death not ascertained, employment elsewhere in the vanadium industry, and exposure to a known carcinogenic agent during a period of employment elsewhere. Males and females were included and participants were not excluded on the basis of race or ethnicity. Employees of all ages were eligible. Exposure assessment at both plants was based on recorded V2O5 concentrations in personal air samples, the participant’s job history, the history of vanadium processing, the physical structure and work organisation at the processing plants. Historical V2O5 concentrations in air in the workplace were retrospectively estimated for those periods during which personal air sampling was not conducted. Historical concentrations were estimated by extrapolation from current (known) air concentrations, in conjunction with data on annual production volumes, personal experiences of occupational hygienists and plant managers at the plant, and historical records of plant upgrades, controls on emissions, changes in production processes and industrial incidents and accidents, where available at the plants. Exposure was expressed as the cumulative exposure (mg-years/m3) and the mean air concentration (mg/m3) of V2O5 to which participants had been exposed. Study participants were also classified into exposure categories based on their mean exposure concentrations. Results In total, 196 questionnaires were collected from eligible participants. The majority (94.4 per cent) were males. Smoking and the consumption of alcohol was fairly common amongst the study group, with 61 per cent of the participants being current or previous smokers, and 59.5 per cent indicating that they were drinking alcoholic drinks or beverages. The mean age (± SD) of the study group was 52.4 ± 10.2. The annual mean exposure of the study group during the period of employment was 0.02 ± 0.03 mg/m3 V2O5, and the mean cumulative exposure to V2O5 was 0.17 ± 0.46 mg-years/m3. Four (4) cancer cases were confirmed at the South African plant, and 6 at the USA plant: four adenocarcinomas (three each in the prostate and one in the colon); three squamous cell carcinomas (two each in the lung and one skin cancer); one renal cell cancer of the kidney, one seminoma of the testis, and one papillary urothelial cancer of the bladder. The occurrence of prostate and lung cancers were not unusual, giving the presence of risk factors such as relatively advanced age (for prostate cancer) and smoking (for lung cancer). The other types of cancer, and the ages at which cancer was most frequently diagnosed (the mean age at diagnosis of cancer was 58.5) were not remarkably different from those that were prominent in the cancer literature. An unusual cluster of specific types of cancer, or of any prominent and unusual organ involvement not associated with known non-occupational risk factors, was therefore not found in the case group. Conclusion The results of this study fail to indicate a statistically significant association between cancer and various indices of exposure to vanadium pentoxide. This conclusion is subject to a number of limitations and uncertainties arising from the small number of cases available for study, and limited follow-up of some participants. The potential association between exposure and cancer should be tested in a larger study group with more cancer cases, allowing more powerful statistical analyses, ideally multivariate logistic regression analysis. The study has confirmed the feasibility of the retrospective assessment of exposure to vanadium compounds in the vanadium processing industry, providing that the processing plant history covers detail of processing methodologies, physical structures, production volumes and work organisation, and providing that a detailed job history should be available for all potential participants. Confirmation of the cause of death and cancer status of previous employees was not practical in the South African scenario. An open case-control design nested in a prospective cohort should be more successful in the South African scenario, but also more expensive and results will only be available after an extended follow-up period. In the USA scenario tracing of previous employees, and access to cancer registries and death certificates should be more practical, and a retrospective case-control study should be possible. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / School of Health Systems and Public Health (SHSPH) / Unrestricted

O presente trabalho consiste na preparação e caracterização de filmes finos de óxido nióbio (Nb2O5) dopados com trifluoro metano sulfonato de lítio (CF3SO3Li). A adição do sal de lítio tem como objetivo verificar a influência do mesmo nas performances opto-eletroquímicas dos filmes de óxido de nióbio. Os sóis para deposição dos filmes foram preparados pelo processo sol-gel submetendo a mistura de NbCl5, butanol, ácido acético e o sal de lítio à irradiação ultra-sônica por alguns minutos. Em seguida, os filmes foram depositados pela técnica dip-coating sobre um substrato de vidro recoberto com camada condutora (ITO-Asahi). Os filmes foram então submetidos a um tratamento térmico entre 400&#176C e 600&#176C durante alguns minutos em atmosfera de ar. A reversibilidade eletroquímica destes filmes foi estudada através de voltametria cíclica e cronoamperometria. As medidas de transmissão ótica foram realizadas in-situ na região entre 350 e 800nm (ultravioleta ao visível). Análises microscópicas (MEV, EDX, AFM) foram feitas para verificar a textura, composição e a topografia dos filmes. Foram feitas também, medidas de espectroscopia de infravermelho para a caracterização dos sóis e análises térmicas (DTA/TGA) e difração de raios-X para os precipitados. O possível uso destes filmes em sistemas eletrocrômicos para aplicação em arquitetura foi estudado através de comparação com os resultados de transmissão ótica de vidros comuns. / Present work shows the preparation and characterization of niobium (V) oxide films (Nb2O5) doped with lithium trifluoromethanesulfonate (CF3SO3Li). The main objective of lithium salt addition was to verify its influence on the opto-electrochemical performance of the niobia films. Sols to deposition of the films were prepared by sol-gel process. The mixture of NbCl5 butanol, acetic acid and lithium salt was submitted to ultrasonic irradiation for some minutes. After, films were deposited by dip-coating on glass substrate re-covered with conductor layer (ITO-Asahi). Films were submitted to the thermal treatment between 400 and 600&#176C during some minutes in air atmosphere. The electrochemical reversibility of these films was studied by cyclic voltammetry and chronoamperometry. Their optical transmission measurements were performed in-situ in the UV-VIS range (between 350 and 800nm). Microscopic analysis (SEM, EDX, AFM) was made to check the texture, composition and topography of the films. Infrared spectroscopy measurements were made to sols characterizations and thermal analyses (TGA/ DTA) and X-ray diffraction to the precipitates. The possible use these films in architecture was studied by comparing with the optic transmission results of the common glass.

The quadrupolar interaction in sodium orthovanadate dodecahydrate, calcium orthovanadate, vanadinite, descloizite, zirconium divanadate, cadmium divanadate, potassium metavanadate and vanadium pentoxide, was studied by nuclear magnetic resonance. The v51 quadrupole coupling constants in these compounds show a strong correlation with the distortion of the tetrahedral symmetry around the vanadium ion. Vanadium pentoxide is an exception and shows a surprisingly small coupling constant. The point multipole model was found to be inadequate for the calculations of the electric field gradients in these compounds. A covalent model provides an explanation of the small magnitude of the coupling constant of vanadium pentoxide. However, because of the numbers of approximations in this model, only a qualitative correlation with the experimental results was achieved. In addition, the chemical shift tensor of the v51 resonance line in a single crystal of vanadium pentoxide was measured to be very large. This result was correlated with a large Van Vleck term in the magnetic susceptibility of vanadium pentoxide. / Thesis / Doctor of Philosophy (PhD)

Made available in DSpace on 2017-07-21T20:43:48Z (GMT). No. of bitstreams: 1 Felipe Holtz de Andrade.pdf: 6124468 bytes, checksum: f5473082aa79c46a8a2ec002b3185a19 (MD5) Previous issue date: 2015-08-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The purpose of this work is the synthesis and characterizations of a glass foam using sodium hydroxide as the foaming agent, in addition to niobium pentoxide used as filler. For the synthesis of the foam, waste glass, sodium hydroxide and niobium pentoxide were mixed in a mold, dried and sintered at 800 oC. In follow, the foam was characterized by different methods: X-ray diffraction (XRD), thermogravimetric and diferential scanning calorimetry (DSC), Helium pycnometry, compression testing, high resolution electron microscopy field-emission gun (FEG) and chemical microanalysis energy dispersive x-ray spectroscopy (EDS). The result obtained was a glass foam with 36,50 % of porosity and 44,50 % increase in the compressive strenght by niobium pentoxide. / A proposta deste trabalho consistiu na síntese e caracterização de uma espuma constituída de vidro moído e hidróxido de sódio como agente espumante, além do pentóxido de nióbio utilizado como agente de carga. Para a síntese da espuma, o resíduo de vidro, hidróxido de sódio e pentóxido de nióbio foram misturados em um molde, secados e sinterizados a 800 oC. Em seguida, a espuma foi caracterizada por diferentes ensaios: difração de raios X (DRX), análise termogravimétrica e varredura diferencial de calorimetria (DSC), picnometria de Hélio, ensaio de compressão,microscopia eletrônica de varredura de alta resolução (FEG) e microanálise química por níveis de energia (EDS). Obteve-se uma espuma de vidro com porosidade de 36,50 % e aumento de 44,50 % na resistência a compressão pelo pentóxido de nióbio.

A utilização de novas rotas de síntese de materiais nanoestruturados tem levado à obtenção de materiais apresentando novas propriedades e aplicações. O presente trabalho teve como principal objetivo realizar a síntese e a caracterização de nanopartículas de óxido de vanádio obtidas pelo método da decomposição de peróxido utilizando o tratamento hidrotermal. Por meio do controle do tempo e da temperatura de síntese, foi possível obter nanoestruturas de pentóxido de vanádio com diferentes fases cristalinas e morfologias. Os resultados de espectroscopia Raman e difração de raios X (DRX) mostraram que o tratamento hidrotermal da solução em temperaturas de até 180oC, durante 2 horas, leva à formação da fase V2O5nH2O monoclínica, apresentando uma orientação preferencial na direção 00l. A partir desta temperatura, o material obtido passou a ter a fase ortorrômbica perdendo sua orientação preferencial. Através das medidas de termogravimetria (TG) foi observado que, dependendo da condição de síntese, as amostras apresentam diferentes quantidades de moléculas de água (H2O) intercaladas em sua estrutura. Imagens de microscopia eletrônica mostraram que as nanoestruturas obtidas podem possuir a forma de fitas, fios ou bastões. Utilizando a técnica de espectroscopia de absorção de raios X (XAS), foi possível verificar a presença de íons de V4+ nas amostras de fase monoclínica, o que não foi observado naquelas que possuem estrutura ortorrômbica. Pela técnica de XAS também foi possível constatar que as amostras de estrutura ortorrômbica possuem menor grau de desordem ao redor do átomo de vanádio. O estudo do mecanismo de crescimento da nanoestrutura de V2O5nH2O mostrou que ocorre um crescimento lateral, o qual pode ser descrito pelo mecanismo denominado Coalescência Orientada ou Oriented attachment (OA). Finalmente, através da decomposição do peróxido de vanádio, foi possível obter compostos vanadatos contendo cátions de Na+ em sua estrutura. / The use of new routes for nanostructured materials synthesis has lead to materials with new properties and applications. This PhD project aimed to realize the synthesis and the characterization of vanadium pentoxide nanoparticles obtained by peroxide decomposition using the hydrothermal treatment. By controlling synthesis time and temperature it was possible to achieve vanadium pentoxide nanoparticles with different crystalline phases and orphologies. The results of Raman spectroscopy and X-ray diffraction (XRD) showed that the hydrothermal treatment of the solution at temperatures up to 180oC for two hours leads to formation of the V2O5nH2O monoclinic phase with a preferential orientation on 00l direction. From this temperature on the material obtained began to present the orthorhombic phase misleading its preferential orientation. Through thermogravimetry (TG) measurements it was seen that depending on the synthesis condition the samples contains different amounts of water molecules (H2O) interleaved in their structure. Images of transmission electron microscopy (TEM) showed that the V2O5nH2O compound could have different morphologies such as ribbons, wires and rods. From X-Ray Absorption spectroscopy (XAS) measurements, it was observed the presence of V4+ ions in the monoclinic phase samples, which was not observed on orthorhombic structure samples. Through the XAS technique was also observed that the orthorhombic structure samples have a lower degree of disorder around the vanadium atom. Regarding the growth mechanism of these nanostructures, it was possible to verify that has been a wide growth which can be explained by the mechanism denominated Oriented Attachment (OA). Finally, through vanadium peroxide decomposition vanadates compounds containing Na+ cation in its structure were carried out.

O presente trabalho utilizou a técnica de automontagem camada-por-camada para produzir eletrodos híbridos de poli(o-metoxianilina) e nanopartículas de pentóxido de vanádio. Foram obtidos filmes acusticamente rígidos, homogêneos com relação à massa depositada e com crescimento linear com o número de bicamadas depositadas. A caracterização eletroquímica foi realizada por voltametria cíclica, onde esse filme apresentou alta capacidade de intercalação/desintercalação de íons lítio e de forma reversível. A capacidade eletroquímica desse filme foi então comparada com filmes automontados de poli(dialildimetilamônio)/V2O5 e polialilamina/V2O5. O filme de Poli(dialildimetilamônio) apresentou um crescimento irregular com dissolução das nanopartículas, o que resultou em uma capacidade eletroquímica extremamente inferior ao filme de poli(o-metoxianilina). O filme de polialilamina apresentou uma deposição mais eficiente de V2O5 que o filme de poli(o-metoxianilina), entretanto essa maior quantidade de pentóxido de vanádio não refletiu em um aumento da capacidade do eletrodo. Os resultados de espectroscopia de impedância eletroquímica mostram que o filme de polialilamina é significativamente mais resistivo que o filme de poli(o-metoxianilina). Essa diminuição da condutividade, associada ao fato de que a poli(o-metoxianilina) também participa do processo de eletrointercalação, explicam seu melhor desempenho frente a intercalação de lítio. A difusão iônica do lítio nos filmes automontados foi estudada por varredura linear a diferentes velocidades, foi observado que o coeficiente de difusão no filme com polialilamina é uma ordem de grandeza menor que no filme de poli(o-metoxianilina). Por fim, o desempenho eletroquímico do filme de poli(o-metoxianilina)/V2O5 foi comparado no eletrólito composto por um líquido iônico hidrofóbico [bis(trifluorometanosulfonil)imideto de 1-butil-2,3-dimetil-imidazólio] com um solvente orgânico convencional (carbonato de propileno). O eletrodo se mostrou estável no líquido iônico, com maior capacidade específica e menor perda de capacidade. O desempenho superior ao eletrólito convencional está relacionado com a natureza iônica do líquido iônico e com a dissolução do filme em carbonato de propileno. Esses resultados, associados com o fato de que o líquido iônico estudado é compatível com ânodos de lítio metálico, indicam cátodos de poli(o-metoxianilina)/V2O5 em eletrólitos de (bis(trifluorometanosulfonil)imideto de 1-butil-2,3-dimetil-imidazólio podem desenvolver baterias de lítio de alta capacidade, durabilidade e segurança. / The present work used layer-by-layer technique to assemble hybrid electrodes of poly(o-methoxyaniline) and vanadium pentoxide nanoparticles. The film obtained was acoustically rigid, with homogeneous mass deposition and linear growth over the bilayer deposition. The electrochemical characterization was performed by cyclic voltammetry and the film showed high capacity for lithium intercalation and high reversibility in the extraction process. This film\'s capacity was compared with self-assembled poly(diallyldimetylammonium)/V2O5 and polyallylamine/V2O5. In the poly(diallyldimetylammonium) film, dissolution of the nanoparticles was observed, which reflected on a very low electrochemical capacity. The deposition of vanadium pentoxide was more efficient in polyallylamine, but even with a higher amount of V2O5, this electrode presented a smaller electrochemical capacity than poly(o-methoxyaniline)/ V2O5. Electrochemical impedance spectroscopy measurements showed that the film with polyallylamine was much more resistive than the film with poly(o-methoxyaniline). The smaller conductivity and the fact that poly(o-methoxyaniline) also participates in the electroinsertion processes explains the higher performance of poly(o-methoxyaniline)/ V2O5 electrode. Linear sweep experiments with different scan rates were performed to study the chemical diffusion of lithium in the layer-by-layer films. It was observed that the diffusion coefficient in the polyallylamine film is ten times smaller than in the poly(o-methoxyaniline) film. The capacity poly(o-methoxyaniline)/V2O5 electrode was also compared in different electrolytes; a hydrophobic ionic liquid [1-butyl- 2,3-dimethyl-imidazolium bis(trifluoromethanesulfonyl)imide] and an organic solvent (propylene carbonate). In ionic liquid the film was stable, had higher capacity and better cyclability, which is related to the ionic nature of the electrolyte and the fact that in propylene carbonate, dissolution of the film was observed. These results, and the possibility of using metallic lithium as anode in [1-butyl-2,3-dimethyl-imidazolium bis(trifluoromethanesulfonyl)imide], indicates the feasibility of using ionic liquids and poly(o-methoxyaniline)/V2O5 cathodes in safe, durable and high performance lithium batteries.

A utilização de novas rotas de síntese de materiais nanoestruturados tem levado à obtenção de materiais apresentando novas propriedades e aplicações. O presente trabalho teve como principal objetivo realizar a síntese e a caracterização de nanopartículas de óxido de vanádio obtidas pelo método da decomposição de peróxido utilizando o tratamento hidrotermal. Por meio do controle do tempo e da temperatura de síntese, foi possível obter nanoestruturas de pentóxido de vanádio com diferentes fases cristalinas e morfologias. Os resultados de espectroscopia Raman e difração de raios X (DRX) mostraram que o tratamento hidrotermal da solução em temperaturas de até 180oC, durante 2 horas, leva à formação da fase V2O5nH2O monoclínica, apresentando uma orientação preferencial na direção 00l. A partir desta temperatura, o material obtido passou a ter a fase ortorrômbica perdendo sua orientação preferencial. Através das medidas de termogravimetria (TG) foi observado que, dependendo da condição de síntese, as amostras apresentam diferentes quantidades de moléculas de água (H2O) intercaladas em sua estrutura. Imagens de microscopia eletrônica mostraram que as nanoestruturas obtidas podem possuir a forma de fitas, fios ou bastões. Utilizando a técnica de espectroscopia de absorção de raios X (XAS), foi possível verificar a presença de íons de V4+ nas amostras de fase monoclínica, o que não foi observado naquelas que possuem estrutura ortorrômbica. Pela técnica de XAS também foi possível constatar que as amostras de estrutura ortorrômbica possuem menor grau de desordem ao redor do átomo de vanádio. O estudo do mecanismo de crescimento da nanoestrutura de V2O5nH2O mostrou que ocorre um crescimento lateral, o qual pode ser descrito pelo mecanismo denominado Coalescência Orientada ou Oriented attachment (OA). Finalmente, através da decomposição do peróxido de vanádio, foi possível obter compostos vanadatos contendo cátions de Na+ em sua estrutura. / The use of new routes for nanostructured materials synthesis has lead to materials with new properties and applications. This PhD project aimed to realize the synthesis and the characterization of vanadium pentoxide nanoparticles obtained by peroxide decomposition using the hydrothermal treatment. By controlling synthesis time and temperature it was possible to achieve vanadium pentoxide nanoparticles with different crystalline phases and orphologies. The results of Raman spectroscopy and X-ray diffraction (XRD) showed that the hydrothermal treatment of the solution at temperatures up to 180oC for two hours leads to formation of the V2O5nH2O monoclinic phase with a preferential orientation on 00l direction. From this temperature on the material obtained began to present the orthorhombic phase misleading its preferential orientation. Through thermogravimetry (TG) measurements it was seen that depending on the synthesis condition the samples contains different amounts of water molecules (H2O) interleaved in their structure. Images of transmission electron microscopy (TEM) showed that the V2O5nH2O compound could have different morphologies such as ribbons, wires and rods. From X-Ray Absorption spectroscopy (XAS) measurements, it was observed the presence of V4+ ions in the monoclinic phase samples, which was not observed on orthorhombic structure samples. Through the XAS technique was also observed that the orthorhombic structure samples have a lower degree of disorder around the vanadium atom. Regarding the growth mechanism of these nanostructures, it was possible to verify that has been a wide growth which can be explained by the mechanism denominated Oriented Attachment (OA). Finally, through vanadium peroxide decomposition vanadates compounds containing Na+ cation in its structure were carried out.